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Stratton, G. E. and D. C. Lowrie, 1984. Courtship behavior and life cycle of the wolf spidQi Schizo- 
cosa mccooki (Araneae, Lycosidae). J. Arachnol., 12:223-228. 


COURTSHIP BEHAVIOR AND LIFE CYCLE OF THE 
WOLF SPIDER SCHIZOCOSA MCCOOKI 
(ARANEAE, LYCOSIDAE) 


Gail E. Stratton^ 

Department of Biological Sciences 
University of Cincinnati 
Cincinnati, Ohio 45221 

and 


Donald C. Lowrie 

Rte. 2, Box 305-76 
Sante Fe, New Mexico 87501 


ABSTRACT 

Individuals of Schizocosa mccooki (Montgomery) are found in open areas of pinyon-juniper 
woodland in New Mexico. They co-occur with individuals of Alopecosa kochi (Keyserling) and 
Lycosa colomdensis Banks. Individuals of S. mccooki overwinter as immatures. They then mature in 
May, and mating occurs in May and June. During courtship, a male S, mccooki will make a quick 
jump, assume a position facing the female, and perform a series of palpal movements. The pattern of 
sound production includes a series of 2-18 bursts of percussion, with each burst consisting of 24 
individual taps of the palps. The sounds produced from a courtship sequence of two individuals from 
Saskatchewan, Canada, were very similar to the sounds produced by the individuals from New Mexico. 


INTRODUCTION 

Schizocosa mccooki (Montgomery, 1904) is a medium-sized wolf spider common 
throughout the western United States. Its reported range is from southern Canada to 
central Mexico, from the Pacific Ocean, east to mid-Texas and in the northeast, to Michi- 
gan (Dondale and Redner 1978). Don dale and Redner (1978) describe S. mccooki as 
abundant, widespread, and variable. S. mccooki has typically been collected by pitfall 
traps (Allred 1975) or by headlamp collecting, as reported here. The preferred habitats of 
X mccooki appear to be open ground or small desert shrubs in pinyon pine-juniper 
woodland, in grass and sedge as on the shore of Lake Erie (Dondale and Redner 1978), or 
in dry grassland (Buckle 1972). A brief description of the courtship can be found in 
Buckle (1972) (misidentified as S. avida) and Uetz and Stratton (1982). The present 

^Current address: Dept, of Biology, Bradley University, Peoria, Illinois 61625. 


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THE JOURNAL OF ARACHNOLOGY 


Study was undertaken to examine aspects of courtship of S. mccooki quantitatively, to 
compare the courtship of S. mccooki from New Mexico with the courtship of S. mccooki 
from Saskatchewan, Canada, and to describe the life cycle of S, mccooki from New 
Mexico. 


METHODS 

Individuals of S. mccooki were collected in pinyon-juniper woodland, in an approxi- 
mately 5 km^ area on the southwest border of Santa Fe, Sante Fe Co., New Mexico. 
Collecting was done with a headlamp, from early evening, after sundown, until midnight. 
In order to reduce sampling bias, each specimen that was seen was pursued until captured. 
Each night’s catch was identified, sexed if mature, and carapace width was measured 
(Hagstrum 1971). The number of individuals collected in one evening varied from 0 to 20 
spiders. Collections were made from April through November, after which time condi- 
tions were such that no spiders were seen. Means and 95% confidence intervals for cara- 
pace width were calculated for each month’s collections. 

In June 1979, 25 individuals (4 males and 21 females) were collected. These spiders 
were transported to Ohio, where courtship studies were done. Spiders were housed 
individually in plastic rectangular containers (7 cm X 7 cm X 13 cm), and were fed 
crickets (Acheta domestica) or mealworms (Tenebrio molitor) twice weekly. Each was 
supplied with a cotton-plugged water vial as a source of moisture. All courtship observa- 
tions were made in June 1979. 

Courtship behavior of three males was recorded on film with a Nizo Super 8 movie 
camera (speed 54 fps.) Sound and vibration recordings were made of all four courting 
males with a Bruel and Kjaer accelerometer (Type 4366) high sensitivity vibration pickup 
leading to a Bruel and Kjaer sound level meter (Type 2203). The output was recorded by 
a Teac tape recorder (model 2300) which had a frequency response range of 40 Hz to 24 
kHz. All recordings were made at 19.05 cm/sec (7.5 ips). The accelerometer was placed 
on a piece of paper which had served as a cage liner for a female S. mccooki. To obtain a 
visual representation of the sound, tapes were played through a recording oscilloscope. 
The tapes were also played through a Bruel and Kjaer sound level recorder (Type 2304), a 
high speed recording instrument designed for the measurement of signal level variations. 
Portions of the recordings of S. mccooki have been deposited at the Borrer Library of 
Bioacoustics at The Ohio State University, Columbus, Ohio. 

A tape of the courtship of two individuals of S. mccooki from southwestern Saskatch- 
ewan, Canada was obtained from D. J. Buckle. Quantitative comparisons of these individ- 
uals were made with the New Mexico specimens. Details of the recording procedure are in 
Buckle (1972). 



Fig. 1. -Position of male Schizocosa mccooki during sound production. 


STRATTON AND LOWRIE -COURTSHIP AND LIFE HISTORY m SCHIZOCOSA 


225 


RESULTS AND DISCUSSION 

Courtship Behavior,— The male S, mccooki responded with courtship in the presence 
of a conspecific female. Courtship began immediately following the first physical contact 
between male and female. In three or four instances, the male did not respond with 
courtship when presented with only the female’s cageliner (which held the female’s silk, 
and possible a pheromone). No chemoexploring (movement of the dorsum of the palp on 
the substrate — Tietjen 1977) was observed. 

Analysis of high speed film showed that a typical courtship sequence began with the 
male making a quick jump, assuming a position facing the female with his venter flush 
with the substrate (Fig. 1), and then performing a series of palpal drums. This drumming 
has been called “bursts of percussion” (Uetz and Stratton 1982), or “tapping palpi on the 
substrate with nearly contiguous strums” (Buckle 1972). The movement was reported as 
“stridulatory sounds” by Dondale and Redner (1978). The palps were in contact with the 
substrate except when the drumming occurred. The primary movement of the palp was 
clearly percussive, with the entire palp moving up and down. In some instances, the palps 
were raised and lowered together, but usually the palps were drummed in an alternating 
sequence. While drumming, the male spider made no movement with the rest of his 
body. High-speed-film analysis indicated an occasional oscillation of the palp that was 
similar to the movement made during stridulation in other species of Schizocosa and 
Lycosa (Rovner 1975, Stratton and Uetz 1981, 1983). However, if stridulation (passing a 
scraper across a file) was occurring it was not detected with the recording techniques and 
analysis used. Clearing and mounting the male palp and examining it microscopically 
indicated a stridulatory organ is present. Thus, the relative importance of percussion and 
stridulation in this species remain untested. 

The pattern of sound production consists of a series of 2 to 18 bursts, each burst 
including 2 to 4 individual taps of the palps. The overall pattern of sounds is shown in 
Fig, 2. Of the New Mexico spiders a series consisted of 2 to 18 bursts (x = 6.5 bursts/ 
series) with an average length of 5.2 seconds/series, and separated from the next series by 
an average of 26.9 seconds. The average time between bursts of percussion was 1.4 
seconds (Table 1). The individuals from Canada showed an average of 6.1 bursts/series, an 
average duration of 3.3 seconds/series, and separated from the next series by an average 
of 21.5 seconds. The average time between bursts of percussion was 1.9 seconds. Even 
though the sample size of spiders is not sufficient to permit statistical comparisons, it is 
clear that the percussive patterns in the courtship of the two populations are very similar. 
Although dines in many characters are known (Endler 1977), dines in behaviors have not 
been extensively studied. This type of quantitative description will permit further com- 


Table 1.- Quantitative comparison of the courtship of Schizocosa mccooki collected from New 
Mexico and Saskatchewan, Canada (means are indicated ± 2 S.D.). 


Geographic 

Locality 

Number of bursts 
per series 

Duration of a 
series (sec) 

Interseries 
interval (sec) 

Burst rate 
(burst/sec) 

New Mexico 

6.5 ± 4,4 

5,2 ±4.4 

26.9 

1.46 ±0.82 

(4 males) 

n = 28 

n= 14 

n= 2 

n = 14 

Saskatchewan 

6.1 ± 8,5 

3.3 ±5.2 

21.5 ±45.6 

1.9 ± 1.44 

(2 males) 

n = 28 

n= 28 

n = 28 

n = 28 


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THE JOURNAL OF ARACHNOLOGY 


parisons of courtship behavior in this species over a geographic range. Attempts at inter- 
breeding between the two populations would provide the ultimate test of whether the 
courtship patterns are the same, or are similar enough to allow interbreeding {ie., that 
they are indeed the same species and not “cryptic” species, sensu Walker 1964). 

Habitat and Life Cycle.— Specimens of S. mccooki were mostly found in the open 
areas of a pinyon-juniper woodland. Although they were occasionally collected among 
small shrubs, such as snakeweed (Gutierrezia sarothrae), or rabbit brush (Chrysothamnus 
nauseosus). One of us (DCL) has collected S. mccooki elsewhere in the west and found it 
to occur in sagebrush meadows. Collections showed that S, mccooki overlapped little 
with sympatric species of wolf spiders in their preferred habitats, toc/z/ (Key- 

serling) was found only beneath trees, and Lycosa coloradensis Banks built burrows in 
open areas between pinyons and junipers (Lowrie, unpub. data). 

Adult males and females of S. mccooki can be found from May through October. 
Collections indicated that 96% of the animals matured vdthin a week of each other. Most 
matings probably occur in late May and June. Egg sacs are laid, carried and hatch in July. 
Individuals overwinter as immatures, and mature the follovdng spring. The spiders are 
occasionally active on warmer days in the winter; thus, they are not true hibernators but 
are quiescent in the cold. Although the number of instars in S. mccooki is not known, the 

Drumming courtship sequence of Schizocosa mccooki . 


a series 

with 18 bursts interseries 



H 

0. 1 25 sec 


Fig. 2. —Courtship sequence of S. mccooki. Sequence of 50 seconds, showing series of bursts of 
percussion and interseries intervals. Inset is sequence of 1.25 second showing three bursts, with 24 
taps of the palps in each burst. 


STRATTON AND LOWRIE-COURTSHIP AND LIFE HISTORY IN SCHIZOCOSA 


227 


CARAPACE WIDTH AS FUNCTION OF AGE 

Horizontal Line = Mean 
Vertical Line = Actual Range 
Box = 95% Confidence Interval 



Fig. 3. -Carapace width of S. mccooki as a function of month of collection. 


growth of the species through the growing season is indicated by carapace width (Hag- 
strum 1971) (Fig. 3). Curiously, the carapace width of immature spiders collected in 
the spring was less than the carapace width of those collected in the fall. As this cannot 
be a reduction in the size of individuals, it can probably be attributed to a small collec- 
tion sample in April. 

Mature males were slightly smaller than mature females (mean carapace width in mm: 
male x = 3.04, N = 10; female x = 3.23, N = 48). The size of the New Mexico population 
was smaller than the figures reported by Dondale and Redner (1978) (mean carapace 
width, male x = 4.06, N = 131 ; female x = 4.46, N = 153). 

CONCLUSIONS 

This study provides a description of the sounds produced by S, mccooki during 
courtship. The importance of these sounds has not yet been experimentally demon- 
strated; however, the apparent lack of visual signals (the male moves little during a 
courtship bout) suggests that the acoustic signals are important. The natural substrate 
used by male S. mccooki in courtship is unknown but of interest. It is possible that the 
vegetation on which the spiders are sometimes found could be used during courtship as a 


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substrate which conducts the vibrational signals. The other possibility is that the spiders 
are on the bare ground (which is bare of leaflitter). How the substrate is used by the 
spiders and what selection pressures exist for drumming and stridulating are intriguing 
questions awaiting further investigation. 

ACKNOWLEDGMENTS 

The acoustic recordings and filming were done in the laboratory of Dr. G. W. Uetz. 
Drs. G. W. Uetz, W. P. Aspey, J. S. Rovner, and W. J. Tietjen and R. Bjorklund provided 
helpful comments on the manuscript. To these people we extend sincere thanks. Thanks 
is also extended to D. J. Buckle for loan of the tape recording of S. mccooki from Sas- 
katchewan, Canada. 


LITERATURE CITED 

Allred, D. M. 1975. Arachnids as ecological indicators. Gt. Basin Nat., 35:405-06. 

Buckle, D. J. 1972. Sound production in the courtships of two lycosid spiders Schizocosa avida 
Walckenaer and Tarentula aculeata (Clerck). The Blue Jay, 30:110-13. 

Dondale, C. D. and J. H. Redner. 1978. Revision of the nearctic wolf spiders genus Schizocosa (Aran- 
eida: Lycosidae). Canadian Ent., 110:143-81. 

Endler, J. A. 1977. Geographic variation, speciation and clines. Princeton University Press, New 
Jersey, 246 pp. 

Hagstrum, D. W. 1971. Carapace width as a tool for evaluating the rate of development of spiders in 
the laboratory and field. Ann. Ent. Soc. America, 64(4): 75 7-60. 

Rovner, J. S. 1975. Sound production by Nearctic wolf spiders: A substratum-coupled stridulatory 
mechanism. Science, 190:1309-10. 

Stratton, G. E. and G. W. Uetz. 1981. Acoustic communication and reproductive isolation in two 
species of wolf spiders. Science, 214:575-77. 

Stratton, G. E. and G. W. Uetz. 1983. Communication via substratum-coupled stridulation and repro- 
ductive isolation in wolf spiders (Araneae: Lycosidae). Anim. Behav., 31:164-72. 

Tietjen, W. J. 1977. Dragline following by male lycosid spiders. Psyche, 84:165-78. 

Uetz, G. W. and G. E. Stratton. 1982. Acoustic communication and reproductive isolation in spiders. 
In Spider communication; mechanisms and ecological significant. P. N. Witt and J. S. Rovner, eds. 
Princeton University Press. 

Walker, T. J. 1964. Cryptic species among sound-producing ensiferan Orthoptera (Gryllidae and 
Tettigoniidae). Quart. Rev. Biol., 39:345-55. 


Manuscript received May 1983, revised October 1983.